Though it says taconsulting.com is available but it's registered.
Also when I click the namecheap affiliate link it would be nice if it landed on the domain search page with the chosen domain as the keyword.
Not sure where you are doing the whois to see if the domain is registered. It seem pretty inaccurate.
I'm not sure yet what is causing the problem. It could be that someone just registered the domain because i cache the results for a few minutes.. or the api I use produces too many bad results.. I will hopefully figure it out.
Your other point is already on my todo list and will be implemented soon. I'm still in the process of unifying different affiliate merchants.. using some of them directly, some via CJ makes things ugly (code wise).
I've worked with CJ apis before and they were pretty bad.
Just to update you. Some affiliate links (e.g. namecheap) now redirect directly to the corresponding domain.
I've also changed the domain availability check from the api I used before to a homegrown dns ns lookup. This is not 100% accurate too but seems to be better and a lot faster until now!